Unfortunately ABYC doesn't provide an exemption for this. Most of their language assumes the only invertors used will be inverter chargers and have a link to shorepower.
They never actually address this scenario shorepower exists but it is not in any way connected to the inverter. Per the black and white letter of the regs all invertors should detect shorepower connection and disconnect neutral and ground when shorepower is connected.
The only exception listed is using an isolation transformer.
Does it make sense? Probably not. Are their edge cases which don't fit in their rules? Certainly.
Note this same edge case would apply even if you only had one inverter for example shorepower connected to nothing but a
charger. No other connection to anything. Seperate from that you have an inverter which provides AC loads on the
boat and has no connection to shorepower at all. Per ABYC regs even in this scenario it would need a neutral/ground bond based on shorepower connection. Again the one exception would be using an isolation transformer. It gets more dubious when you consider that some (most)
marine chargers have an isolation transformer. So a
charger connected to an isolation transformer is treated one way but a charger with a built in isolation transformer is treated another way.